U.S. patent number 10,416,696 [Application Number 16/191,355] was granted by the patent office on 2019-09-17 for low dropout voltage regulator.
This patent grant is currently assigned to RichWave Technology Corp.. The grantee listed for this patent is RichWave Technology Corp.. Invention is credited to Chih-Sheng Chen, Tien-Yun Peng.
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United States Patent |
10,416,696 |
Chen , et al. |
September 17, 2019 |
Low dropout voltage regulator
Abstract
A power supply device includes an input terminal, a regulated
voltage output terminal, a switch, a first transistor, and a
current split circuit. The input terminal receives a first control
voltage. The regulated voltage output terminal outputs an output
voltage. The switch has a first terminal coupled to the input
terminal, a second terminal, and a control terminal. The first
transistor has a first terminal coupled to a voltage terminal, a
second terminal coupled to the regulated voltage output terminal,
and a control terminal coupled to the second terminal of the
switch. The current split circuit is coupled to the voltage
terminal and the regulated voltage output terminal. The current
split circuit receives the first control voltage or a second
control voltage, and includes a second transistor coupled between
the voltage terminal and the regulated voltage output terminal.
Inventors: |
Chen; Chih-Sheng (Taipei,
TW), Peng; Tien-Yun (Taipei, TW) |
Applicant: |
Name |
City |
State |
Country |
Type |
RichWave Technology Corp. |
Taipei |
N/A |
TW |
|
|
Assignee: |
RichWave Technology Corp.
(Taipei, TW)
|
Family
ID: |
66633046 |
Appl.
No.: |
16/191,355 |
Filed: |
November 14, 2018 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20190163220 A1 |
May 30, 2019 |
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Foreign Application Priority Data
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Nov 28, 2017 [TW] |
|
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106141387 A |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G05F
1/462 (20130101); G05F 1/575 (20130101); G05F
1/59 (20130101); G05F 1/569 (20130101); G05F
1/595 (20130101) |
Current International
Class: |
G05F
1/59 (20060101); G05F 1/575 (20060101); G05F
1/595 (20060101); G05F 1/569 (20060101); G05F
1/46 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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201414190 |
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Apr 2014 |
|
TW |
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201606472 |
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Feb 2016 |
|
TW |
|
Primary Examiner: Ahmed; Yusef A
Assistant Examiner: Jamali; Ishrat F
Attorney, Agent or Firm: Hsu; Winston
Claims
What is claimed is:
1. A low dropout voltage regulator comprising: an operational
amplifier device configured to output a control voltage according
to an input voltage, a power supply device comprising: an input
terminal configured to receive the control voltage; a regulated
voltage output terminal configured to output an output voltage; a
first switch having a first terminal coupled to the input terminal,
a second terminal, and a control terminal; a first transistor
having a first terminal coupled to a first voltage terminal, a
second terminal coupled to the regulated voltage output terminal,
and a control terminal coupled to the second terminal of the first
switch; and a current split circuit coupled to the first voltage
terminal, the input terminal, and the regulated voltage output
terminal, and comprising a second transistor coupled between the
first voltage terminal and the regulated voltage output terminal;
and a feedback circuit coupled to the regulated voltage output
terminal and the operational amplifier device.
2. The low dropout voltage regulator of claim 1, wherein: when a
cross voltage between the first terminal and the second terminal of
the first transistor is greater than an endurable threshold of the
first transistor, the first switch is turned off and the output
voltage is outputted by the current split circuit; and when the
cross voltage between the first terminal and the second terminal of
the first transistor is smaller than the endurable threshold of the
first transistor, the first switch is turned on and the output
voltage is outputted at least by the first transistor.
3. The low dropout voltage regulator of claim 2, wherein the
endurable threshold of the first transistor is smaller than a
breakdown voltage of the first transistor.
4. The low dropout voltage regulator of claim 1, wherein the
operational amplifier device comprises an operational amplifier
having a first input terminal configured to receive the input
voltage, a second input terminal, and an output terminal configured
to output the control voltage; wherein the current split circuit is
coupled to the input terminal for receiving the control
voltage.
5. The low dropout voltage regulator of claim 1, further
comprising: a second switch having a first terminal coupled to the
first voltage terminal, a second terminal coupled to the control
terminal of the first transistor, and a control terminal; wherein:
the first transistor is a P-type transistor; when a cross voltage
between the first terminal and the second terminal of the first
transistor is greater than an endurable threshold of the first
transistor, the first switch is turned off and the second switch is
turned on; and when the cross voltage is smaller than the endurable
threshold, the first switch is turned on and the second switch is
turned off.
6. The low dropout voltage regulator of claim 1, further
comprising: a second switch having a first terminal coupled to a
second voltage terminal, a second terminal coupled to the control
terminal of the first transistor, and a control terminal; wherein:
the first transistor is an N-type transistor; when a cross voltage
between the first terminal and the second terminal of the first
transistor is greater than an endurable threshold of the first
transistor, the first switch is turned off and the second switch is
turned on; and when the cross voltage is smaller than the endurable
threshold, the first switch is turned on and the second switch is
turned off.
7. The low dropout voltage regulator of claim 1, wherein: the
current split circuit further comprises a third switch having a
first terminal coupled to the input terminal, a second terminal
coupled to a control terminal of the second transistor, and a
control terminal; when a cross voltage between the first terminal
and the second terminal of the first transistor is greater than an
endurable threshold of the first transistor, the third switch is
turned on; and when the cross voltage is smaller than the endurable
threshold, the third switch is turned off.
8. The low dropout voltage regulator of claim 7, wherein: the
current split circuit further comprises a fourth switch having a
first terminal coupled to the first voltage terminal, a second
terminal coupled to the control terminal of the second transistor,
and a control terminal; the second transistor is a P-type
transistor; when the cross voltage is greater than the endurable
threshold, the fourth switch is turned off; and when the cross
voltage is smaller than the endurable threshold, the fourth switch
is turned on.
9. The low dropout voltage regulator of claim 7, wherein: the
current split circuit further comprises a fourth switch having a
first terminal coupled to a second voltage terminal, a second
terminal coupled to the control terminal of the second transistor,
and a control terminal; the second transistor is an N-type
transistor; when the cross voltage is greater than the endurable
threshold, the fourth switch is turned off; and when the cross
voltage is smaller than the endurable threshold, the fourth switch
is turned on.
10. The low dropout voltage regulator of claim 1 further comprising
a control circuit, wherein: the control circuit is configured to
control the first switch according to an endurable threshold of the
first transistor, and one of the output voltage and a cross voltage
between the first terminal and the second terminal of the first
transistor; or the control circuit is configured to control the
first switch according to a current flowing through the regulated
voltage output terminal.
11. The low dropout voltage regulator of claim 1, wherein: the
second transistor has a first terminal coupled to the first voltage
terminal, a second terminal, and a control terminal coupled to the
input terminal; and the current split circuit further comprises a
voltage drop element having a first terminal coupled to the second
terminal of the second transistor, and a second terminal coupled to
the regulated voltage output terminal.
12. The low dropout voltage regulator of claim 11, wherein a
channel width-to-length ratio of the first transistor is greater
than a channel width-to-length ratio of the second transistor.
13. The low dropout voltage regulator of claim 1, wherein: the
current split circuit further comprises a voltage drop element
having a first terminal coupled to the first voltage terminal, and
a second terminal; and the second transistor has a first terminal
coupled to the second terminal of the voltage drop element, a
second terminal coupled to the regulated voltage output terminal,
and a control terminal coupled to the input terminal.
14. The low dropout voltage regulator of claim 13, wherein a
channel width-to-length ratio of the first transistor is greater
than a channel width-to-length ratio of the second transistor.
15. The low dropout voltage regulator of claim 1, wherein a channel
length of the second transistor is greater than a channel length of
the first transistor.
16. A low dropout voltage regulator comprising: an operational
amplifier device configured to output at least a first control
voltage according to an input voltage, a power supply device
comprising: an input terminal configured to receive the first
control voltage; a regulated voltage output terminal configured to
output an output voltage; a first switch having a first terminal
coupled to the input terminal, a second terminal, and a control
terminal; a first transistor having a first terminal coupled to a
first voltage terminal, a second terminal coupled to the regulated
voltage output terminal, and a control terminal coupled to the
second terminal of the first switch; and a current split circuit
coupled to the first voltage terminal, the operational amplifier
device, and the regulated voltage output terminal, and the current
split circuit comprising a second transistor coupled between the
first voltage terminal and the regulated voltage output terminal;
and a feedback circuit coupled to the regulated voltage output
terminal and the operational amplifier device.
17. The low dropout voltage regulator of claim 16, wherein: the
operational amplifier device comprises: a first operational
amplifier having a first input terminal configured to receive the
input voltage, a second input terminal, and an output terminal
configured to output the first control voltage; and a second
operational amplifier having a first input terminal configured to
receive the input voltage, a second input terminal, and an output
terminal coupled to the current split circuit and configured to
output a second control voltage to control the current split
circuit; and the feedback circuit comprises: a first feedback unit
coupled to the regulated voltage output terminal and the second
input terminal of the first operational amplifier; and a second
feedback unit coupled to the regulated voltage output terminal and
the second input terminal of the second operational amplifier.
18. A power supply device comprising: an input terminal configured
to receive a first control voltage; a regulated voltage output
terminal configured to output an output voltage; a first switch
having a first terminal coupled to the input terminal, a second
terminal, and a control terminal; a first transistor having a first
terminal coupled to a first voltage terminal, a second terminal
coupled to the regulated voltage output terminal, and a control
terminal coupled to the second terminal of the first switch; and a
current split circuit coupled to the first voltage terminal and the
regulated voltage output terminal, and configured to receive the
first control voltage or a second control voltage, the current
split circuit comprising a second transistor coupled between the
first voltage terminal and the regulated voltage output
terminal.
19. The power supply device of claim 18, wherein the first control
voltage and the second control voltage are provided by an
operational amplifier device, and the output voltage is configured
to supply power to a power amplifier.
20. The power supply device of claim 18, wherein: when a current
flowing through the regulated voltage output terminal is greater
than a threshold, the first switch is turned on and the output
voltage is outputted by at least the first transistor; and when the
current flowing through the regulated voltage output terminal is
smaller than the threshold, the first switch is turned off and the
output voltage is outputted by the current split circuit.
Description
CROSS REFERENCE TO RELATED APPLICATION
This application claims priority of Taiwan application No.
106141387, which was filed on Nov. 28, 2017, and is included herein
by reference.
TECHNICAL FIELD
This invention is related to a low dropout voltage regulator, and
more particularly, to a low dropout voltage regulator capable of
protecting the internal transistor from breaking down.
BACKGROUND
In prior art, low dropout voltage regulators are commonly used to
supply power for circuits. Therefore, in a low dropout voltage
regulator, the transistor for outputting power has to endure great
current loading, and has to be implemented with a great area. In
addition, since the circuit may be switched between different
operation modes, the output voltage and output current of the low
dropout voltage regulators will also change. If the variations of
the voltage and current are rather severe and exceed the safe
operating area (SOA) of the transistor in the low dropout voltage
regulator, then the transistor would break down, causing abnormal
behavior of the low dropout voltage regulator and even damaging the
low dropout voltage regulator.
For example, in the wireless communication application, the low
dropout voltage regulator can provide power for the power
amplifier. When the power amplifier is to be changed from a high
power mode to a low power mode, the low dropout voltage regulator
can lower its output voltage so the power of the power amplifier
can be lowered accordingly. However, in this case, the cross
voltage endured by the transistor in the low dropout voltage
regulator will increase, and may exceed the SOA of the transistor
easily, causing instability to the system.
SUMMARY
One embodiment of the present invention discloses a low dropout
voltage regulator. The low dropout voltage regulator includes an
operational amplifier device, a power supply device, and a feedback
circuit.
The operational amplifier device outputs a control voltage
according to an input voltage. The power supply device includes an
input terminal, a regulated voltage output terminal, a switch, a
first transistor, and a current split circuit. The input terminal
receives the control voltage. The regulated voltage output terminal
outputs an output voltage. The switch has a first terminal coupled
to the input terminal, a second terminal, and a control terminal.
The first transistor has a first terminal coupled to a voltage
terminal, a second terminal coupled to the regulated voltage output
terminal, and a control terminal coupled to the second terminal of
the switch. The current split circuit is coupled to the voltage
terminal, the input terminal, and the regulated voltage output
terminal, and includes a second transistor coupled between the
voltage terminal and the regulated voltage output terminal. The
feedback circuit is coupled to the regulated voltage output
terminal and the operational amplifier device.
Another embodiment of the present invention discloses a low dropout
voltage regulator. The low dropout voltage regulator includes an
operational amplifier device, a power supply device, and a feedback
circuit.
The operational amplifier device outputs at least a control voltage
according to an input voltage. The power supply device includes an
input terminal, a regulated voltage output terminal, a switch, a
first transistor, and a current split circuit. The input terminal
receives the control voltage. The regulated voltage output terminal
outputs an output voltage. The switch has a first terminal coupled
to the input terminal, a second terminal, and a control terminal.
The first transistor has a first terminal coupled to a voltage
terminal, a second terminal coupled to the regulated voltage output
terminal, and a control terminal coupled to the second terminal of
the switch. The current split circuit is coupled to the voltage
terminal, the operational amplifier device, and the regulated
voltage output terminal, and the current split circuit includes a
second transistor coupled between the voltage terminal and the
regulated voltage output terminal. The feedback circuit is coupled
to the regulated voltage output terminal and the operational
amplifier device.
Another embodiment of the present invention discloses a power
supply device. The power supply device includes an input terminal,
a regulated voltage output terminal, a switch, a first transistor,
and a current split circuit.
The input terminal receives a first control voltage. The regulated
voltage output terminal outputs an output voltage. The switch has a
first terminal coupled to the input terminal, a second terminal,
and a control terminal. The first transistor has a first terminal
coupled to a voltage terminal, a second terminal coupled to the
regulated voltage output terminal, and a control terminal coupled
to the second terminal of the switch. The current split circuit is
coupled to the voltage terminal and the regulated voltage output
terminal. The current split circuit receives the first control
voltage or a second control voltage, and includes a second
transistor coupled between the voltage terminal and the regulated
voltage output terminal.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a low dropout voltage regulator according to one
embodiment of the present invention.
FIG. 2 shows a safe operating area of the first transistor of the
low dropout voltage regulator in FIG. 1.
FIG. 3 shows a power supply device according to another embodiment
of the present invention.
FIG. 4 shows a power supply device according to another embodiment
of the present invention.
FIG. 5 shows a power supply device according to another embodiment
of the present invention.
FIG. 6 shows a power supply device according to another embodiment
of the present invention.
FIG. 7 shows a power supply device according to another embodiment
of the present invention.
FIG. 8 shows a power supply device according to another embodiment
of the present invention.
FIG. 9 shows a power supply device according to another embodiment
of the present invention.
FIG. 10 shows a low dropout voltage regulator according to another
embodiment of the present invention.
DETAILED DESCRIPTION
Below, exemplary embodiments will be described in detail with
reference to accompanying drawings so as to be easily realized by a
person having ordinary knowledge in the art. The inventive concept
maybe embodied in various forms without being limited to the
exemplary embodiments set forth herein. Descriptions of well-known
parts are omitted for clarity, and like reference numerals refer to
like elements throughout.
FIG. 1 shows a low dropout voltage regulator 10 according to one
embodiment of the present invention. The low dropout voltage
regulator 10 can include an operational amplifier device 11, a
feedback circuit 12, and a power supply device 100.
The operational amplifier device 11 can output a control voltage
Vctrl according to an input voltage Vin. In FIG. 1, the operational
amplifier device 11 can include an operational amplifier OP1. The
operational amplifier OP1 has a first input terminal, a second
input terminal, and an output terminal. The first input terminal of
the operational amplifier OP1 can receive the input voltage Vin,
and the output terminal of the operational amplifier OP1 can output
the control voltage Vctrl.
The power supply device 100 can include an input terminal IN, a
regulated voltage output terminal OUT, a switch SW1A, a transistor
M1P, and a current split circuit 110. The input terminal IN can be
coupled to the output terminal of the operational amplifier OP1 in
the operational amplifier device 11 to receive the control voltage
Vctrl. The switch SW1A has a first terminal, a second terminal, and
a control terminal. The first terminal of the switch SW1A can be
coupled to the input terminal IN. The transistor M1P has a first
terminal, a second terminal, and a control terminal. The first
terminal of the transistor M1P is coupled to a voltage terminal
NV1, the second terminal of the transistor M1P is coupled to the
regulated voltage output terminal OUT, and the control terminal of
the transistor M1P is coupled to the second terminal of the switch
SW1A. The current split circuit 110 is coupled to the voltage
terminal NV1, the input terminal IN, and the regulated voltage
output terminal OUT. The current split circuit 110 includes a
transistor M2P coupled between the voltage terminal NV1 and the
regulated voltage output terminal OUT. A voltage V1 provided by the
voltage terminal NV1 can be a high voltage in the system, such as a
battery voltage in the system.
In FIG. 1, the current split circuit 110 can further include a
voltage drop element 112. The transistor M2P has a first terminal,
a second terminal, and a control terminal. The first terminal of
the transistor M2P is coupled to the voltage terminal NV1, and the
control terminal of the transistor M2P is coupled to the input
terminal IN for receiving the control voltage Vctrl outputted by
the operational amplifier OP1 of the operational amplifier device
11. The voltage drop element 112 has a first terminal and a second
terminal. The first terminal of the voltage drop element 112 is
coupled to the second terminal of the transistor M2P, and the
second terminal of the voltage drop element 112 is coupled to the
regulated voltage output terminal OUT. In FIG. 1, the voltage drop
element 112 can be implemented by a transistor. The voltage drop
element 112 further includes a control terminal, and the control
terminal of the voltage drop element 112 can be coupled to the
control terminal of the transistor M2P.
The regulated voltage output terminal OUT can output the output
voltage Vo, and the feedback circuit 12 can be coupled to the
regulated voltage output terminal OUT and the operational amplifier
device 11. The feedback circuit 12 includes a feedback unit FB1
coupled to the regulated output terminal OUT, the second input
terminal of the operational amplifier OP1, and a voltage terminal
NV2. A voltage V2 provided by the voltage terminal NV2 can be a low
voltage or a ground voltage in the system.
In some embodiments of the present invention, the output voltage Vo
outputted by the low dropout voltage regulator 10 can be provided
to other circuits as a power supply, and the low dropout voltage
regulator 10 can choose the internal paths for outputting the
output voltage Vo according to the condition of the circuit
receiving the output voltage Vo.
For example, in FIG. 1, the output voltage Vo outputted by the low
dropout voltage regulator 10 can be provided to the power amplifier
PA as a power supply. When the power amplifier PA operates in a
high power mode, the low dropout voltage regulator 10 would provide
a higher output voltage Vo, for example, the output voltage Vo may
be close to the voltage V1 provided by the voltage terminal NV1. In
this case, since the first terminal of the transistor M1P is
coupled to the voltage terminal NV1, the cross voltage V.sub.DS
between the first terminal and the second terminal of the
transistor M1P is rather small. FIG. 2 shows a safe operating area
(SOA) of the transistor M1P. According to FIG. 2, when the cross
voltage V.sub.DS between the first terminal and the second terminal
of the transistor M1P is rather small, the transistor M1P is able
to provide a greater current I.sub.DS within the SOA without
breaking down. Therefore, when the cross voltage V.sub.DS between
the first terminal and the second terminal of the transistor M1P is
rather small, the switch SW1A can be turned on, so the transistor
M1P would receive the control voltage Vctrl to produce the output
voltage Vo. That is, in this case, the output voltage Vo is mainly
provided by the transistor M1P.
Contrarily, when the power amplifier PA operates in a low power
mode, the low dropout voltage regulator 10 would provide a lower
output voltage Vo, which can be as low as the low voltage or the
ground voltage of the system. For example, if the voltage V1
provided by the voltage terminal NV1 is the battery voltage at
4.2V, then the output voltage Vo provided by the low dropout
voltage regulator 10 can be about 0.2V when operating in the low
power mode. Since the first terminal of the transistor M1P is
coupled to the voltage terminal NV1, the cross voltage V.sub.DS
between the first terminal and the second terminal of the
transistor M1P would be about 4V. However, as shown in FIG. 2, when
the cross voltage V.sub.DS of the transistor M1P is rather large,
the transistor M1P may only generate a small current, otherwise,
the transistor M1P may be outside its SOA, breaking down the
transistor M1P.
In addition, in a common manufacturing process, the breakdown
voltage of the transistor M1P might be 1.8V or 3.3V. In this case,
if the output voltage Vo is outputted by the transistor M1P, making
the transistor M1P to generate current when the cross voltage
V.sub.DS is 4V, then the transistor M1P might breakdown, causing
instability to the system. Therefore, when the cross voltage
V.sub.DS of the transistor M1P is rather large, the switch SW1A can
be turned off, and the output voltage Vo would be outputted by the
current split circuit 110. Since the current split circuit 110
includes the transistor M2P and the voltage drop element 112, these
two elements can endure part of the cross voltage respectively,
refraining the transistor M2P from breaking down.
Also, since the output current is smaller when the output voltage
Vo is smaller, the channel width-to-length ratio of the transistor
M2P can be smaller than the channel width-to-length ratio of the
transistor M1P for reducing the area required by the power supply
device 100. In some embodiments, the channel width-to-length ratio
of the transistor M1P can be 10 times greater than the channel
width-to-length ratio of the transistor M2P. However, the size of
the transistors can be decided according to the system requirement
in other embodiments.
In some embodiments, the power supply device 100 can set up the
endurable threshold of the transistor M1P according to its SOA, and
the endurable threshold can be determined to be smaller than the
breakdown voltage of the transistor M1P, ensuring the transistor
M1P to operate in the SOA. When operating, the cross voltage
V.sub.DS between the first terminal and the second terminal of the
transistor M1P can be compared with the endurable threshold of the
transistor M1P as the base to control the switch SW1A. That is, the
power supply device 100 can turn off the switch SW1A and output the
output voltage Vo through the current split circuit 110 when the
cross voltage V.sub.DS between the first terminal and the second
terminal of the transistor M1P is greater than the endurable
threshold of the transistor M1P. Also, the power supply device 100
can turn on the switch SW1A and output the output voltage Vo
through the transistor M1P when the cross voltage V.sub.DS between
the first terminal and the second terminal of the transistor M1P is
smaller than the endurable threshold of the transistor M1P. In this
case, although the split current 110 may continue to generate the
output voltage Vo, the output voltage Vo would still be outputted
mainly by the transistor M1P due to the larger effective conducting
resistance of the transistor M2P. Namely, in this case, the output
voltage Vo would be outputted at least by the transistor M1P.
Furthermore, since the first terminal of the transistor M1P is
coupled to the voltage terminal NV1 for receiving a fixed system
voltage, the cross voltage V.sub.DS endured by the transistor M1P
can be derived by detecting the voltage at the second terminal of
the transistor M1P, that is, by detecting the output voltage Vo, in
some embodiments. For example, in FIG. 1, the power supply device
100 can further include a control circuit 120. The control circuit
120 can determine whether the cross voltage V.sub.DS of the
transistor M1P is greater than the endurable threshold of the
transistor M1P according to the voltage at the second terminal of
the transistor M1P, that is, the output voltage Vo, and control the
switch SW1A accordingly.
Also, the output voltage Vo of the low dropout voltage regulator 10
is related to the input voltage Vin of the operational amplifier
device 11, for example, the ratio of the output voltage Vo and the
input voltage Vin is usually fixed. In this case, the control
circuit 120 can also derive the cross voltage V.sub.DS endured by
the transistor M1P by detecting to the input voltage Vin, and use a
comparator to compare the relation between the cross voltage
V.sub.DS of the transistor M1P and the endurable threshold of the
transistor M1P for controlling the switch SW1A.
Since the power supply device 100 can control the internal path for
generating the output voltage Vo according to the cross voltage
V.sub.DS of the transistor M1P, the current split circuit 110 can
be used to generate the output voltage Vo when the output voltage
Vo is rather low and the cross voltage V.sub.DS of the transistor
M1P is too high, protecting the transistor M1P from falling out of
the SOA and breaking down, and improving the system stability.
In FIG. 1, the control circuit 120 can derive the cross voltage
V.sub.DS of the transistor M1P by detecting the output voltage Vo,
however, in some other embodiments, since the current flowing
through the regulated voltage output terminal OUT, that is, the
output current, is also related to the output voltage Vo, the
control circuit 120 may also use the current flowing through the
regulated voltage output terminal OUT for determination and
control.
FIG. 3 shows the power supply device 200 according to another
embodiment of the present invention. The power supply devices 100
and 200 have similar structures and can be operated by similar
principles. However, the power supply device 200 further includes a
current detection element 230. The current detection element 230
can transform the output current Io flowing through the regulated
voltage output terminal OUT into a voltage signal. Consequently,
the control circuit 220 would be able to determine the status of
the transistor M1P according to the intensity of the output current
Io, and to turn on or turn off the switch SW1A accordingly,
ensuring the transistor M1P to operate in its SOA.
For example, the user can determine the threshold according to the
SOA of the transistor M1P and the relation between the output
current Io and the output voltage Vo. When the current flowing
through the regulated voltage output terminal OUT, that is, the
output current Io, is greater than the threshold, the control
circuit 220 would turn on the switch SW1A so the output voltage Vo
would be outputted mainly by the transistor M1P. When the current
flowing through the regulated voltage output terminal OUT is
smaller than the threshold, the control circuit 220 would turn off
the switch SW1A so the output voltage Vo would be outputted by the
current split circuit 110.
In FIG. 1, the transistor M1P can be a P-type transistor. To ensure
the transistor M1P will not generate current when the switch SW1A
is turned off, the power supply device 100 can further include
other switches for controlling the circuit in some embodiments.
FIG. 4 shows a power supply device 300 according to another
embodiment of the present invention. The power supply devices 100
and 300 have similar structures and can be operated by similar
principles. However, the power supply device 300 further includes a
switch SW2A. The switch SW2A has a first terminal, a second
terminal, and a control terminal. The first terminal of the switch
SW2A is coupled to the voltage terminal NV1, the second terminal of
the switch SW2A is coupled to the control terminal of the
transistor M1P. When the cross voltage V.sub.DS between the first
terminal and the second terminal of the transistor M1P is greater
than the endurable threshold of the transistor M1P, the switch SW1A
would be turned off and the switch SW2A would be turned on.
Therefore, the control terminal of the transistor M1P would be
coupled to the voltage terminal NV1 through the switch SW2A, and
will not be turned on unexpectedly due to being floating.
Contrarily, when the cross voltage V.sub.DS of the transistor M1P
is smaller than the endurable threshold of the transistor M1P, the
switch SW1A would be turned on and the switch SW2A would be turned
off.
In FIG. 4, the control terminal of the switch SW2A can be coupled
to the control circuit 320. In other words, the control circuit 320
can control the switch SW1A and the switch SW2A at the same time.
However, in other embodiments of the present invention, the
switches SW1A and SW2A can also be controlled by different control
circuits. That is, the control circuit 320 can control at least one
of the switches SW1A and SW2A according to the system
requirement.
FIG. 5 shows a power supply device 400 according to another
embodiment of the present invention. The power supply devices 300
and 400 have similar structures, and can be operated by similar
principles. However, the current split circuit 410 of the power
supply device 400 further includes a switch SW3A and a switch
SW4A.
The switch SW3A has a first terminal, a second terminal, and a
control terminal. The first terminal of the switch SW3A can be
coupled to the input terminal IN for receiving the control voltage
Vctrl outputted by the operational amplifier device 11, and the
second terminal of the switch SW3A is coupled to the control
terminal of the transistor M2P. When the cross voltage V.sub.DS
between the first terminal and the second terminal of the
transistor M1P is greater than the endurable threshold of the
transistor M1P, the switch SW3A would be turned on. In this case,
the output voltage Vo would be generated by the current split
circuit 410. When the cross voltage V.sub.DS of the transistor M1P
is smaller than the endurable threshold of the transistor M1P, the
switch SW3A would be turned off. In this case, the output voltage
Vo would be generated by the transistor M1P.
The switch SW4A has a first terminal, a second terminal, and a
control terminal. The first terminal of the switch SW4A can be
coupled to the voltage terminal NV1, and the second terminal of the
switch SW4A is coupled to the control terminal of the transistor
M2P. In FIG. 5, the transistor M2P is a P-type transistor.
Therefore, when the cross voltage V.sub.DS of the transistor M1P is
smaller than the endurable threshold of the transistor M1P, the
switch SW4A would be turned on. In this case, the control terminal
of the transistor M2P would be fixed at the voltage V1 provided by
the voltage terminal NV1, so the transistor M2P would not be turned
on unexpectedly due to being floating. Contrarily, when the cross
voltage V.sub.DS of the transistor M1P is greater than the
endurable threshold of the transistor M1P, the switch SW4A would be
turned off. In other words, when the transistor M1P is turned on,
the transistor M2P would be turned off.
In FIG. 5, the control terminals of the switches SW1A, SW2A, SW3A,
and SW4A can all be coupled to the control circuit 420. In other
words, the control circuit 420 can control the switches SW1A, SW2A,
SW3A, and SW4A at the same time. However, in other embodiments of
the present invention, the switches SW1A, SW2A, SW3A, and SW4A can
also be controlled by different control circuits. That is, the
control circuit 420 can control at least one of the switches SW1A,
SW2A, SW3A, and SW4A according to the system requirement. Also, in
some embodiments of the present invention, the power supply device
400 can remove the switches SW2A and SW4A according to the system
requirement. In this case, the control circuit 420 can control at
least one of the switches SW1A and SW3A.
In addition, the control circuit 420 can be aware of the cross
voltage V.sub.DS of the transistor M1P according to the output
voltage Vo and compare the cross voltage V.sub.DS of the transistor
M1P with the endurable threshold of the transistor M1P for
controlling the switches as the control circuit 120 shown in FIG.
1. However, in other embodiments, the control circuit 420 can also
detect the cross voltage V.sub.DS of the transistor M1P directly
and compare the cross voltage V.sub.DS of the transistor M1P with
the endurable threshold of the transistor M1P, or the control
circuit 420 can control the switches by sensing the output current
Io as done by the control circuit 220 shown in FIG. 3.
In the embodiments in FIGS. 1 and 3 to 5, the voltage drop element
112 can be implemented by a transistor. However, in other
embodiments, the voltage drop element 112 can also include at least
one transistor, a resistor, at least one diode, at least one
diode-connected transistor, or any combinations of the four
aforementioned items. In addition, connection order of the voltage
drop element 112 and the transistor M2P can be changed.
FIG. 6 shows a power supply device 500 according to another
embodiment of the present invention. The power supply devices 400
and 500 have similar structures and can be operated by similar
principles. However, in the power supply device 500, the current
split circuit 510 can include a transistor M2P, a voltage drop
element 512, a switch SW3A and a switch SW4A. The voltage drop
element 512 has a first terminal and a second terminal. The first
terminal of the voltage drop element 512 is coupled to the voltage
terminal NV1. The transistor M2P has a first terminal, a second
terminal, and a control terminal. The first terminal of the
transistor M2P is coupled to the second terminal of the voltage
drop element 512, the second terminal of the transistor M2P is
coupled to the regulated voltage output terminal OUT, and the
control terminal of the transistor M2P can be coupled to the input
terminal IN through the switch SW3A.
In addition, in FIG. 6, the voltage drop element 512 can include N
diode-connected transistors MD coupled in series, where N is an
integer and N.gtoreq.2. In other embodiments, the diode-connected
transistors MD in the voltage drop element 512 can be replaced by
diodes. Or, the voltage drop element 512 can further include
resistors or transistors, or the combination of at least one of the
resistor, the transistor, the diode, and the diode-connected
transistor.
In addition, in some embodiments, the voltage drop elements 112 and
512 can be omitted. FIG. 7 shows a power supply device 600
according to another embodiment of the present invention. The power
supply devices 400 and 600 have similar structures and can be
operated by similar principles. However, in the power supply device
600, although the current split circuit 610 includes a transistor
M2P' and switches SW3A and SW4A, it does not include other voltage
drop elements. In other words, the first terminal of the transistor
M2P' is coupled to the voltage terminal NV1, the second terminal of
the transistor M2P' is coupled to the regulated voltage output
terminal OUT, and the control terminal of the transistor M2P' can
be coupled to the input terminal IN through the switch SW3A for
receiving the control voltage Vctrl outputted by the operational
amplifier device 11. However, the channel length of the transistor
M2P' can be greater than the channel length of the transistor M1P.
In other words, the conducting resistance of the transistor M2P'
would be greater than the conducting resistance of the transistor
M1P, and the transistor M2P' is able to endure a higher voltage
drop.
In the embodiments shown in FIGS. 1 and 3 to 7, the transistors
M1P, M2P or M2P' are all P-type transistors. However, in other
embodiments of the present invention, the user can also implement
the transistors M1P, M2P or M2P' with N-type transistors. FIG. 8
shows a power supply device 700 according to another embodiment of
the present invention. The power supply devices 400 and 700 have
similar structures, and can be operated by similar principles.
However, in the power supply device 700, the transistor M1N, the
transistor M2N in the current split circuit 710, and the voltage
drop element 712 are all implemented by N-type transistors.
In this case, the switches SW2B and SW4B of the power supply device
700 would be coupled to the voltage terminal NV2 providing the
lower voltage. That is, the first terminal of the switch SW2B can
be coupled to the voltage terminal NV2, and the second terminal of
the switch SW2B can be coupled to the control terminal of the
transistor M1N. Also, the voltage V2 provided by the voltage
terminal NV2 can be the ground voltage of the system. Consequently,
when the cross voltage V.sub.DS between the first terminal and the
second terminal of the transistor MIN is greater than the endurable
threshold of the transistor M1N, the switch SW1A would be turned
off, and the switch SW2B would be turned on. Therefore, the control
terminal of the transistor MIN would receive the voltage V2, and
the transistor MIN will not be turned on unexpectedly due to being
floating. Furthermore, when the cross voltage V.sub.DS of the
transistor MIN is smaller than the endurable threshold of the
transistor M1N, the switch SW1A would be turned on, and the switch
SW2B would be turned off.
Similarly, the first terminal of the switch SW4B can be coupled to
the voltage terminal NV2, and the second terminal of the switch
SW4B can be coupled to the control terminal of the transistor M2N.
When the cross voltage V.sub.DS of the transistor MIN is smaller
than the endurable threshold of the transistor M1N, the switch SW3A
would be turned off, and the switch SW4B would be turned on.
Therefore, the control terminal of the transistor M2N would receive
the voltage V2, and the transistor M2N will not be turned on
unexpectedly due to being floating. Also, when the cross voltage
V.sub.DS of the transistor MIN is greater than the endurable
threshold of the transistor M1N, the switch SW3A would be turned
on, and the switch SW4B would be turned off.
In FIG. 8, the control terminals of the switches SW1A, SW2B, SW3A,
and SW4B can be coupled to the control circuit 720. In other words,
the control circuit 720 can control the switches SW1A, SW2B, SW3A,
and SW4B at the same time. However, in other embodiments of the
present invention, the switches SW1A, SW2B, SW3A, and SW4B can also
be controlled by different control circuits. That is, the control
circuit 720 can control at least one of the switches SW1A, SW2B,
SW3A, and SW4B according to the system requirement. Also, in some
embodiments of the present invention, the power supply device 700
can remove the switches SW2B and SW4B according to the system
requirement. In this case, the control circuit 720 can control at
least one of the switches SW1A and SW3A.
In addition, the control circuit 720 can derive the cross voltage
V.sub.DS of the transistor MIN according to the output voltage Vo
as the control circuit 120 shown in FIG. 1, and compare the cross
voltage V.sub.DS of the transistor MIN with the endurable threshold
of the transistor MIN for controlling the switches. However, in
other embodiments, the control circuit 720 can also detect the
cross voltage V.sub.DS of the transistor MIN directly and compare
the cross voltage V.sub.DS of the transistor MIN with the endurable
threshold of the transistor M1N, or the control circuit 720 can
control the switches by sensing the output current Io as done by
the control circuit 220 shown in FIG. 3.
In addition, the present invention is not limited to implementing
the transistors M1P, M2P or M2P' with the same type of transistors.
FIG. 9 shows a power supply device 800 according to another
embodiment of the present invention. The power supply devices 400
and 800 have similar structures, and can be operated by similar
principles. However, in the power supply device 800, the transistor
MIN is an N-type transistor, and the transistor M2P is a P-type
transistor. Generally, the P-type transistor can endure greater
voltage than the N-type transistor, and the N-type transistor has
smaller conducting resistance than the P-type transistor.
Therefore, when the cross voltage V.sub.DS of the transistor MIN is
smaller than the endurable threshold of the transistor M1N, the
switch SW1A would be turned on, the switch SW3A would be turned
off, and the power supply device 800 can output the output voltage
Vo through the transistor M1N. However, when the cross voltage
V.sub.DS between the first terminal and the second terminal of the
transistor M1N is greater than the endurable threshold of the
transistor M1N, the switch SW1A would be turned off, the switch
SW3A would be turned on, and the power supply device 800 can output
the output voltage Vo through the transistor M2P having better
voltage endurability in the current split circuit 410.
Since the power supply device 800 can control the internal path for
generating the output voltage Vo according to the cross voltage
V.sub.DS of the transistor M1N, the power supply device 800 can use
the current split circuit 410 to generate the output voltage Vo
when the output voltage Vo is rather low and the cross voltage
V.sub.DS of the transistor MIN is rather high, protecting the
transistor MIN from falling out of the SOA and breaking down, and
improving the system stability.
In the embodiment shown in FIG. 9, the control terminals of the
switches SW1A, SW2B, SW3A, and SW4A can be coupled to the control
circuit 820. In other words, the control circuit 820 can control
the switches SW1A, SW2B, SW3A, and SW4A at the same time. However,
in other embodiments of the present invention, the switches SW1A,
SW2B, SW3A, and the SW4A can also be controlled by different
control circuits. That is, the control circuit 820 can control at
least one of the switches SW1A, SW2B, SW3A, and SW4A according to
the system requirement. Also, in some embodiments of the present
invention, the power supply device 800 can remove the switches SW2B
and SW4A according to the system requirement. In this case, the
control circuit 820 can control at least one of the switches SW1A
and the SW3A.
The power supply devices 200 to 800 shown in FIGS. 3 to 9 can be
applied to the low dropout voltage regulator 10 shown in FIG. 1 for
replacing the power supply device 100. However, in other
embodiments, the power supply devices 100 to 800 can also be
applied to other different circuits, and can switch their internal
paths for outputting the output voltage according to their output
voltages or output currents.
In addition, in the low dropout voltage regulator 10 in FIG. 1, the
operational amplifier device 11 includes only one operational
amplifier OP1, so the current split circuit 110 and the switch SW1A
would receive the same control voltage Vctrl. However, in some
other embodiments of the present invention, the operational
amplifier device 11 can also include another operational amplifier,
and the current split circuit can receive the control voltage
generated by the another operational amplifier.
FIG. 10 shows a low dropout voltage regulator 20 according to
another embodiment of the present invention. The low dropout
voltage regulator 20 includes the operational amplifier device 21,
the feedback circuit 22, and the power supply device 400.
The operational amplifier device 21 can include operational
amplifiers OP1 and OP2. The operational amplifier OP1 has a first
input terminal, a second input terminal, and an output terminal.
The first input terminal of the operational amplifier OP1 can
receive the input voltage Vin, and the output terminal of the
operational amplifier OP1 can output the control voltage Vctrl. The
operational amplifier OP2 has a first input terminal, a second
input terminal, and an output terminal. The first input terminal of
the operational amplifier OP2 can receive the input voltage Vin,
and the output terminal of the operational amplifier OP2 can be
coupled to the current split circuit 410. The output terminal of
the operational amplifier OP2 can output the control voltage Vctrl'
for controlling the current split circuit 410. The feedback circuit
22 can include the feedback units FB1 and FB2. The feedback unit
FB1 is coupled to the regulated voltage output terminal OUT and the
second input terminal of the operational amplifier OP1. The
feedback unit FB2 is coupled to the regulated voltage output
terminal OUT and the second input terminal of the operational
amplifier OP2.
In other words, the operational amplifiers OP1 and OP2 can operate
in the same status. That is, while the operational amplifier OP1
outputs the control voltage Vctrl to the control terminal of the
transistor M1P, the operational amplifier OP2 can output the
control voltage Vctrl' to the control terminal of the transistor
M2P in the current split circuit 410. The feedback unit FB1 can be
used to provide the feedback signal for the operational amplifier
OP1 to stabilize the control voltage Vctrl generated by the
operational amplifier OP1, and the feedback unit FB2 can be used to
provide the feedback signal for the operational amplifier OP2 to
stabilize the control voltage Vctrl' generated by the operational
amplifier OP2.
Consequently, when the power supply device 400 activates the
current split circuit 410 and uses the transistor M2P to generate
the output voltage Vo, the operational amplifier OP1 will not be
affected, improving the stability of the system.
Furthermore, in the embodiments shown in FIGS. 1 and 3 to 10, the
switches SW1A, SW2A, SW2B, SW3A, SW4A and SW4B can be implemented
by transistors, such as N-type transistors or P-type transistors,
or can be implemented by other electronic components according to
the system requirement.
In summary, the power supply devices and the low dropout voltage
regulators provided by the embodiments of the present invention can
provide power to external circuits, and adjust internal voltage
generating paths according to the status of the external circuits,
protecting the internal transistors from breaking down by high
cross voltages, and improving the stability of the system.
Those skilled in the art will readily observe that numerous
modifications and alterations of the device and method may be made
while retaining the teachings of the invention. Accordingly, the
above disclosure should be construed as limited only by the metes
and bounds of the appended claims.
* * * * *